View Full Version : Stacked 2 subs and was worst!
02-22-2003, 02:37 PM
I have two PSW150s in each corner, but I read where it is recommended to stack them together in a corner, which I did and it killed my bass. Am I missing somethin here? What is the phase switch for? Any advice?
02-22-2003, 04:03 PM
Check the phase switch - are they set the same? Set them both to 0 if they are close to the main speakers.
02-22-2003, 07:43 PM
Dr. Spec if I set tem both the same it is horrible, but If I set one to "REV" and the other to "Norm" it is much better and my Freq is set to "90" and on my pre-amp for my subs. I'm new to this so pardon the ignorance. Dr. Spec is this correct way to set this up? Also, my subs are 14' away from the front speakers. You also metioned in another post about a "Frequency response sweep" and sound meter. Where can I get that file to burn to a cd and what should I do. Like what am I looking for with the above.
02-22-2003, 11:04 PM
How do you have the subs wired? Speaker level? It seems like there might be a wiring mistake if the subs sound much better with one run in REV and the other NORM. Also, how are your speakers electronically set up in the preamp? Let's investigate this first before we move on.
02-22-2003, 11:07 PM
Agreed, if they are stacked, and one is set in reverse phase (180), they should be cancelling each other out more or less.
Why are they so far away from the mains?
02-23-2003, 12:38 AM
I have a B&K Ref 50 Pre-Amp and the subs are attached to the preamp via the sub-out. I put the subs in the rear corner because I thought thats were they are suppose to go. I have read Dr. Specs posts to I'm blue in the face. I have the subs Freq set at 90 and volume about 1/2 way. The bottom subs pahse is set to normal and the one on top is set to rev. If I set them both the same either rev or normal my bass is almost nothing. I have a y-splitter out the back of my pre-amp to the line level inputs of my subs. On the subs I take the cable from the preamp and it is plugged into the right input on both subs w/ a T connector that loops up to the left input on both subs. If you need more information please let me know.
02-23-2003, 12:50 AM
Try moving the stack to where the other one was. I don't know, but it's worth a try.
02-23-2003, 02:10 AM
I spoke to Eric at SVS and I thinkI'm going to purchase the B4-plus! I'm just curious if this will be overkill for my HT room which is 20x16. Also Dr. Spec what amp do you recommend the samson or the crown and will a 1000 watts be enough to drive this sub. My wife will kill me, but hey you only live once.
02-23-2003, 09:26 AM
hi govnah, get another sub for a placement sub, and use the 2 psw-150 as main channel stereo subs with speaker leval hookups, set mains to large. this will help your sound stage.
with the right adjustments & setup it will have a killer sound stage
that the bottem end blends with the placement sub no holes and overwelming bottem.
welcome to the forum.
02-23-2003, 10:14 AM
Originally posted by Govnah
I have a B&K Ref 50 Pre-Amp and the subs are attached to the preamp via the sub-out. I have a y-splitter out the back of my pre-amp to the line level inputs of my subs. On the subs I take the cable from the preamp and it is plugged into the right input on both subs w/ a T connector that loops up to the left input on both subs. If you need more information please let me know.
First, what are your electronic settings for sub and speaker size? For testing purposes, I recommend all speakers set to small, the sub set to on, and the electronic filter point inside the receiver set to 80 Hz (if it is adjustable).
Second, for now, deep six the T-connector that jumps to the left line level input.
For simplicity and testing purposes, run the y-splitter off the preamp sub out and then run a single sub cable to the right line level input of each sub.
Crank the filter control at the subs all the way to its maximum setting.
Repeat the same test with the phase controls. If you get the same results (i.e., they cancel each other out with the same phase setting), I can almost assure you one of the phase switches in one of the subs is wired backwards. Nothing else would explain your results at that point.
Let me know how you make out.
As for the B4 Plus - no it is not overkill in your room. Running a sub well under its limits results in very low THD and tons of headroom. The Samson is not designed to run in bridged mono mode into a 4 ohm load and is inappropriate for this application since the B4+ only has one input cup.
The Crown K1 is a fine amp and should do fine in your room. If you really push the sub hard, you may find 1000 watts to be underpowered. The Crown K2 can be bridged into 4 ohm mono at 2500 watts and may be a better choice depending on your listening tastes.
Remember, doubling the power only results in a 3 dB increase in volume, so going from 1000-2500 watts will only give you maybe 4 dB more headroom, so its not really that extreme as it might seem on the surface.
Other B4 owners are using the QSC-RMX2450 at 2400 watts bridged into 4 ohms with very good results. If I were on a budget, I'd spring for the QSC amp. It can be had for about $600 on-line.
If you buy a B4 Plus, say hi to Erik and Ron over at SVS for me.
02-23-2003, 11:43 AM
Dr. Spec here are the settings on my B&K for my speakers. All speakersare set to small.
High Pass Slope 6db and 12db w/ 12 selected
Cross Over Freq set to 80Hz on the B&K and 150 (which is all the way up.) on the sub. Is this the same as setting the filter?
Low Pass Slop Eternal,6, 12, 24 w/ 24db selected.
Sub Base setting None, yes, ultra w/ yes selected.
Sub Level offset -12db +12db w/ -3db selected.
LFE Attenuation -24db 0db w/ -10db selected (what ever that does.)
All Speaker Level offset is set to 0db except for the sub level which is at -3db
I have also setup the sub in terms off distance frommy listening position. Still have to have one sub set to Norm Phase and the other set to Rev Phase. IfI set them the same it kills the base either Rev or Normal Phase. I have killed the T and just have the interconnect goiing into both right inputs on the subs. My vlume level on the subs is set to 12:00 1/2 way. Hope this helps.
02-23-2003, 02:21 PM
Make sure the filter slope rates are the same for low pass and high pass; you have 12 dB/ocatve selected for high pass and 24 dB/ocatve selected for low pass.
Kill the LFE attentuation - determine how to disable it or failing that set it to 0. It is a dynamic range limiter for the LFE channel.
This will necessitate recalibration most likely.
You will find the bass power and dynamic range much better after killing the LFE limiter and also your transition to the mains will be smoother once your filter rates are the same.
Regardless of the above, and clearly, if they are both stacked and the same phase setting kills the bass, then one of your phase switches is wired backwards. There can be no other explanation, except if someone replaced a driver and wired it backwards, or it was wired backwards from the factory.
02-23-2003, 03:10 PM
I noticed you are the one who posted a blown driver in one of your 150's. Did you replace it recently? Is it possible you wired it backwards? Compare it to the other one if this is the case.
02-23-2003, 05:20 PM
I'm an idiot! had the replacement driver wired wrong. Replaced it and wired correctly and now it sounds fine. Next question Is setting the filter the same as setting the Frequency on the subs. I have the sub frequency set to 80 on the B&K and 80 on the subs. Do I need to change anything and what determines what Phase to select (Rev or Normal.) Also Dr Spec, If you have time can you explain exactly what the frequency setting does or point me in the direction to learn more since I'm new and this is all greek to me? One more question what determines if you select speakers small or large?
02-23-2003, 07:45 PM
Aha! Logic will prevail everytime.
If you are filtering at the receiver, you don't want to do it again at the sub. Set your sub filter all the way up at 150. At that frequency, the receiver has already ensured the sub is getting no signal anyway, so there is nothing left for the sub TO filter.
Basically, when you set your speakers to small, your receiver will start filtering (cutting out) the signal sent to them BELOW a certain frequency (in your case 80 Hz, currently). This is known as "high passing" the speakers.
Then your receiver will start filtering (cutting out) the signal sent to the subwoofer ABOVE a certain frequency (in your case 80 Hz, currently). This is known as "low passing" the subwoofer.
In order to obtain a smooth transition between the speakers and the subwoofer, the receiver will filter the signals on a sloping rate (in your case 12 dB/octave, currently).
So the speakers will play below 80 Hz a little bit, and the sub will play above 80 Hz a little bit. The lower you go, the less the speakers will play, and the higher you go, the less the sub will play. Two octaves below 80 Hz, the speakers will play 24 dB lower in volume. Two octaves above 80 Hz, the sub will play 24 dB lower in volume.
Any speaker you set to large will get a full range signal in that channel with no signal filtered over to the subwoofer. Any speaker set to large should be able to handle a full range signal at whatever volume you prefer for playback.
I personally prefer setting all my speakers to small and filtering at 80 Hz to the sub. My sub can play deeper and stronger than any of my other speakers and can easily handle the bass load from the LFE channel and the combined bass from all the other speaker channels below 80 Hz.
Other people prefer to run some or all of their speakers on large and only send the subwoofer the LFE channel. I don't use this method, but try it both ways and see how you like it.
02-23-2003, 08:31 PM
Dr. Spec you are true asset to mankind to take the time educate people. You have been a big help and I appreciate all the information and help!!!!! All this talk about filtering at 80Hz, is this what what refer to as "Crossover Frequency?"
02-23-2003, 09:25 PM
You're welcome. Make sure to disable that LFE limiter - damn things are insidious bass killers.
Also, if you can, place the stacked 150s in a corner, near the mains. It will help blend the transition between the two. Set the phase switches to 0 in this location.
Finally - calibrate the entire system (including both subs) with a SPL meter to ensure all your speakers are playing at the same volume. That's a topic for another day, though. :-)
02-28-2003, 04:29 AM
Granted that Gonvah needs to go thru a complete SPL balancing of his system, but until then...
With the stacked subs isn't he getting a 3db boost in bass response? If this is the case, isn't setting the LFE out to -3db an appropriate countermeasure?
02-28-2003, 08:03 AM
The LFE is set to -3 to avoid signal distortion from the pre-amp. Its setting is almost otherwise irrelevant with a powered sub.
Stacking subs in the same cormer yields a 6 dB increase in volume.
I think what you were thinking was this: Individually calibrate each sub 3 dB low in relation to the other speakers (e.g. 72/75), and when they are both fired up, it should be 3 dB hot, and just about right. But this adjustment is done at the plate amp, not the receiver.
02-28-2003, 01:35 PM
O-tay... don't think LFE distortion should be a problem with the ref50.
And guess I still don't understand the whole plate amp gain vs. AVR bass output setting, but I am willing to learn...
02-28-2003, 01:58 PM
ANY pre-amp will distort its LFE signal if you push it to +10, just like any amp will clip if you max it out. Quality of the component is not the issue here.
The same issue holds true for all the individual speaker volumes to a similar (but lesser) extent. Go ahead and turn all of them up to +10 (including the LFE) and then play back a dynamic passage at a given safe volume.
Then set them all to zero and play the same passage again (with a correspondingly higher master volume setting to obtain the same overall volume) and see if it sounds more dynamic (less stuffy and compressed). I'm betting with your level of equipment (which is very revealing), you will be able to tell the difference between the two settings.
Clipping a pre-amp signal is no different than clipping an amplifier - the waveform distortion looks identical.
The reason the LFE and/or subwoofer channel is the most important of all the individual volume controls in this regard is because the LFE signal is the most dynamic and is therefore most susceptible to pre-amp clipping if it is set really high (like at +8 or +10).
The key is to avoid extremes at both ends. Setting it too low will unecessarily increase the S/N ratio of the pre-out signal; setting too high (as discussed above) may cause clipping of the waveform.
The reason I suggest a little less than midpoint (-3) is to give the user a little upward adjustability (maybe to 0 or even +1) for music (which is generally less powerful than HT with the sub output) and still leave plenty of breathing room for the LFE pre-amp to not distort the signal via clipping.
The plate amp volume control is the one you want to use to set your final sub volume, much in the same manner as you use your Master Volume control to adjust the volume of all your speakers.
If you send the plate amp a distorted pre-out signal, it will just amplify it and give you distorted bass, even if the plate amp itself is not clipping.
I am passing all of this on from the DIY subwoofers masters on various other forums, and from SVS. All of the above is the overwhelming consensus with the bass gurus.
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